Jason Dufner has played through pain during much of 2014. (Matthew Lewis/Getty Images)

AKRON, Ohio -- Jason Dufner said Wednesday he has been diagnosed with two bulging discs in his neck after undergoing an MRI last Friday.

The reigning PGA champion, who will defend his title next week at Valhalla, first felt pain in his neck the Tuesday of Masters week and thought it was related to a prior shoulder injury because the symptoms were similar.

He has been limited in practice and on Monday received a shot that he hopes will clear up the inflammation. No surgery is needed.

"It makes it pretty tough," Dufner said. "Lack of sleep, lack of motion, lack of strength, a lot of different issues when you're dealing with your neck."

Dufner said the pain level is a "7" on a scale of 1 to 10 and that the worst of it came during the U.S. Open when he wasn't able to sleep the night before the second round.

The 37-year-old is in the field for this week's World Golf Championships-Bridgestone Invitational, where he's looking for his first win of the season after four top 10s, including a runner-up at Colonial in May.